I do think they make a difference.
I see two benefits:
The biggest one is maintaining bottom bracket height. If you want to run a paved and gravel wheelset, the gravel tire wheelset will raise your bottom bracket. Most people prefer a lower bottom bracket for gravel than for paved.
Similar for people who want to run a fat 650b wheel set and skinnier 700c. If you don’t adjust fork offset, you will have less trail with the 650b wheel, but you probably want more trail(since you are using it in sand or rough terrain).
I see less benefit to adjustable chainstay length on a gravel bike. Road bikers like short rear centers. They need those because the front of a road bike is also super short.
As the front center grows (on a gravel bike), so should the rear center.
However, many roadies think that having the rear center on their gravel bike as close as possible to their road bike, will make it handle just like their road bike.
Doing that, they ignore the difference in trail and front center.